EXPERIMENTS IN FIELD PLOT TECHNIC 



41 



The relation of the direction of rows to the effects of varietal com- 

 petition is not clearly shown by these experiments. The tests which 

 showed least the effect of competition, the oats strain test of 1919 

 and the wheat mixture test of 1921, were in rows running north and 

 south. But relatively little effect from competition is to be expected 

 in these tests, regardless of the direction of the rows, because of the 

 similarity of adjacent strains. In the oats strain test 12 of the 15 

 strains were taxonomically identical, and it has been shown that the 

 effects of competition among these was much less than among the 

 strains of different varieties. In the wheat mixture test the varieties 

 making up each mixture, which were grown side by side in the test, 

 were chosen partly for their similarity in time of maturity, and the 

 differences between adjacent varieties were therefore considerably 

 less than in the wheat variety test of the same season. It cannot be 

 stated definitely, therefore, from the results of these tests, that tests 

 in rows running north and south are either more or less subject to error 

 from competition than tests in rows running east and west. It is 

 clear, however, that a considerable error from varietal competition 

 may occur in tests in which the rows run north and south, as is evi- 

 denced particularly by the barley and oats variety tests of 1919. 



The relation of competition to relative date of heading, date of 

 maturity, grain-straw ratio, height, and yield, insofar as it was in- 

 vestigated in these experiments, is shown in summary form in Table 

 17. Although none of these characteristics shows a significant rela- 



17. SUMMARY OF EFFECTS OF COMPETITION IN Au, TESTS. 



tion to competition in every case, the results of the tests are fairly 

 consistent. The correlation of competition with yield is always posi- 

 tive, and is fairly high in every case, the lowest coefficient being +-294 

 .059. From these results there can be no doubt that the higher yield- 

 ing varieties are those which in general have profited by competition. 

 The date of heading and the date of maturity show a negative correla- 



